The Patent Court of Korea Wednesday decided to uphold Pfizer Korea’s patent on its pneumonia vaccine, in a blow to Korean pharmaceutical, SK Chemicals, seeking to launch an independently developed vaccine since last year.

“We are examining the results from the Patent Court of Korea and will proceed with a strategy from our findings,” said a SK Chemicals spokesperson. “As for appealing to the Supreme Court, we have not decided yet, and we will conduct a comprehensive review in regards to launching the vaccine.”

SK Chemicals, the pharmaceutical division of Korean conglomerate SK Group, filed an appeal to the patent court in 2015 to overturn a ruling that validated Pfizer’s patent on Prevnar 13. The dispute began in 2013, with SK Chemicals aiming to invalidate the patent.

In Korea, Pfizer’s Prevnar 13 is the only approved pneumonia vaccine available for all ages, with vaccinations starting at six weeks old for infants. The vaccine protects against 13 pneumococcal serotypes.

The 13-valent vaccine is also one of the only two pneumococcal vaccines produced in the world. No other companies may make cheaper versions of the vaccine until March 2026 – when Pfizer’s Prevnar 13 patent expires.

SK Chemicals has tried to enter the market by successfully developing its pneumonia vaccine SKYPNEUMO but has not been able to launch it despite obtaining the Ministry of Food and Drug Safety’s approval last year.

Experts say that SK Chemicals is limited by both restrictive indications for its vaccine and Pfizer’s hold on relevant patents.

SKYPNEUMO has only been approved to treat adults older than 50, leaving the most critical demographic and most significant profit segment – infants and children – to Prevnar 13.

In fact, Prevnar 13 accounts for about 80 percent of market share in Korea, according to IMS Health. In 2015, revenue totaled approximately 66.2 billion won ($6.02 million).

Meanwhile, international aid group Médecins Sans Frontières criticized Pfizer for holding a monopoly on the development and manufacturing of the pneumonia vaccine. Pfizer has barred competition, allowing the pharmaceutical giant to set unaffordable prices and deprive thousands of getting the vaccination, the group said.

In the U.S., Pfizer recently fell under fire for announcing another price hike for Prevnar 13. The pneumococcal vaccine will rise to around $180 next year, an increase from $169.11 per dose this year and $108.75 in 2010, according to Fierce Pharma.